WASHINGTON — Orders for U.S. factory goods that signal business investment plans jumped last month by the most in more than a year, suggesting companies are confident about their business prospects.

The Commerce Department said Wednesday that orders for so-called core capital goods, which include industrial machinery, construction equipment and computers, rose 6.3 percent in January from December.

A sharp fall in demand for commercial aircraft caused overall durable goods orders to drop 5.2 percent, the first decline since August.

Orders for commercial aircraft are volatile from month to month and can cause large swings in the overall figure. Boeing reported orders for only two planes in January, down from 183 in December.

Orders for defense equipment also plummeted by the most in more than 12 years.

Durable goods are items expected to last at least three years.

The increase in core capital goods suggests companies are willing to expand their production capacities despite worries that automatic government spending cuts will slow the economy in the coming months.

“The fact remains that capital spending appears to be holding up very well,” said Dan Greenhaus, chief global strategist at BTIG, a brokerage firm. “In fact, it appears to be accelerating.”

The report suggests U.S. manufacturing is strengthening, but several economists warned orders were likely to fall in the coming months after such a big gain.

“We don’t expect businesses suddenly to throw caution to the wind,” Paul Ashworth, an economist at Capital Economics, said in a note to clients.

BUSINESS CONFIDENCE: Orders for U.S. factory goods that signal business investment plans jumped last month by the most in more than a year, suggesting companies are confident about their business prospects.

AIRPLANE ORDERS PLUNGE: A sharp fall in demand for commercial aircraft caused overall durable goods orders to drop 5.2 percent, the first decline since August. Such orders are volatile and can cause large swings in the overall figure. Boeing reported orders for only two planes in January, down from 183 in December.

REBOUND: Even with the increase, orders have mostly just recovered last year’s losses. Total core capital goods orders reached $67.7 billion in January, topping December 2011’s level for the first time.